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Reinstalled Windows 10 - how do I reactivate my install?

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Hey everyone,

Last year I performed a free upgrade from windows 8 to windows 10, and yesterday I got a SSD drive and I thought this would've been a good opportunity to clean install my windows on the ssd. But before I did the clean install I wrote down the product key found in the "my pc" properties, but that one only had 20 digits instead of 25. So I installed Produkey to find the product key and it did give me a 25 digit key, but now when I try to activate windows 10 it doesn't work: the product key isn't valid. Could this be the product key for my old windows 8? And why did the windows 10 product key only have 20 digits?

Thanks in advance,


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Hi Nils,

The process isn't perfect but you will be fine. Because the license upgrade was done on another install, you will need to reactivate using the Phone or via Microsoft customer service.

To start, go ahead and install Windows and when prompted for the Product Key, "I don't have a product Key" or, "Do this later". You will be prompted a few times during install.

After you get installed, you need to active. Use this command:

Press Windows key + R then type: slui.exe 4 

It will walk you through the process to reactivate your box.

BTW: Thanks to @adacosta for his write-up on these steps.

Reference: https://www.groovypost.com/howto/transfer-windows-10-license-new-pc


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